1. Field of the Invention
The present invention relates to a technology that my be adopted to reduce the required length of processing time in an electronic camera
2. Description of the Related Art
(Structural Example of Prior Art)
FIG. 6 is a block diagram illustrating the structure of an electronic camera 60 in the prior art.
In FIG. 6, a taking lens 61 is mounted at the electronic camera 60. An image-capturing element 62 is provided in the image space of the taking lens 61. An image output of the image-capturing element 62 is connected to a bus 65 via an A/D conversion circuit 63 and an image processing unit 64.
In addition, the following components are connected to the bus 65:    1 MPU 75 for system control    2 memory 66 that temporarily stores image data and also stores system data managed by the MPU 75    3 JPEG compression/decompression unit 67 that performs compression/decompression of image data    4 thumbnail generating unit 68 that generates thumbnail images    5 image plane (or screen) size conversion unit 69 that generates images for monitor display    6 monitor display circuit 72    7 removable memory 74 for recording image data(Operation Achieved in the Example of the Prior Art)
The following is an explanation of the operation performed in the electronic camera 60.
First, image data obtained through image-capturing performed at the image-capturing element 62 undergo linear quantization via the A/D conversion circuit 63 and then are provided to the image processing unit 64. The image processing unit 64 performs image processing such as defective pixel correction, black level clamping, white balance adjustment, gamma correction, color interpolation processing (two-dimensional image processing under normal circumstances), color space conversion, space filter processing (two-dimensional image processing such as edge emphasis under normal circumstances) and the like on the image data, and the image data having undergone the image processing are temporarily recorded in the memory 66 via the bus 65.
Next, the image plane size conversion unit 69 reads out the image data having undergone image processing by accessing the memory 66 via the bus 65. The image plane size conversion unit 69 reduces the image plane (or screen) size of the image data to the correct size for monitor display and records them in the memory 66 again via the bus 65. The image data having undergone image plane size conversion are again read out from the memory 66 by the monitor display circuit 72 which then displays the image data on the monitor screen.
The thumbnail generating unit 68 accesses the memory 66 via the bus 65 to read out the image data having undergone the image processing. After generating a thumbnail image by reducing the image plane size of the image data, the thumbnail generating unit 68 temporarily records the resulting thumbnail in the memory 66 via the bus 65.
In addition, the JPEG compression/decompression unit 67 reads out the image data having undergone image processing by accessing the memory 66 via the bus 65. The JPEG compression/decompression unit 67 performs a trial compression on the image data and notifies the MPU 75 of the compressed code volume. Based upon a plurality of compressed code volumes provided in this manner, the MPU 75 calculates the correct scale factor (an adjustable parameter that determines the compressed code volume) and issues an instruction to the JPEG compression/decompression unit 67. The JPEG compression/decompression unit 67 reads out the image data having undergone image processing again from the memory 66 via the bus 65 and executes a main compression using the specified scale factor. The compressed data resulting from the main compression are then temporarily recorded in the memory 66 via the bus 65.
Next, the JPEG compression/decompression unit 67 reads out the thumbnail image from the memory 66 via the bus 65 and compresses the thumbnail image. The JPEG compression/decompression unit 67 temporarily records the compressed thumbnail image in the memory 66. Then, the MPU 75 reads out the compressed data from the memory 66 via the bus 65, and generates an image file by combining the compressed data with the compressed thumbnail image. The MPU 75 records this image file in the removable memory 74 via the bus 65.
Through the series of operations described above, image data obtained by capturing images of a subject are sequentially recorded in the removable memory 74.
It is to be noted that while the image plane size conversion, the thumbnail generation and the JPEG compression/decompression are executed by dedicated hardware in the explanation given above, these operations may be achieved through software processing by the MPU 75 if the length of the processing time is not a critical issue.
In this example of the prior art, great volumes of data are repeatedly exchanged via the bus 65 as described above. For this reason, the timing adjustment implemented to avoid data collisions becomes extremely complicated. Furthermore, if the bus 65 cannot assume a sufficiently wide band, the individual processing operations must be executed sequentially.
Thus, a problem arises in that the processing performed in the electronic camera 60 consumes a great deal of time.